Post-extubation Nasal Humidified High-flow Oxygen Versus Non-invasive Positive Pressure Ventilation

Inclusion Criteria: * The study will be recruited on type II respiratory failure patients with difficult weaning from invasive mechanical. Patients who will fulfil the eligibility criteria will be randomly divided into HFNC or NIV groups to receive sequential treatment after extubation. Hypercapnic respiratory failure is defined as an elevation in PaCO2 greater than 45 mmHg and a pH lower than 7.35 resulting from respiratory pump failure and/or production. Type 2 respiratory failure common causes : 1. Neuromuscular Disorders such as: Amyotrophic lateral sclerosis (ALS), Myasthenia gravis, Muscular dystrophy. 2. Spinal cord injuries or damage to the spinal cord that can impair respiratory function. 3. Pulmonary Disorders Like Chronic obstructive pulmonary disease (COPD) ,Cystic fibrosis, Pneumonia Severe infection can cause respiratory failure , Pulmonary embolism. 4. Obesity and Sleep-Related Disorders like Obesity hypoventilation syndrome (OHS), obstructive sleep apnea(OSA). 5. Chest Wall and Pleural Disorders as Kyphoscoliosis, Pleural effusion, Pneumothorax. 6. Other Causes: Sedative overdose, Neurological disorders, high altitude Exclusion Criteria: * 1\. Lack of informed consent. 2. A contraindication to NIV (oral and facial trauma, excessive phlegm with poor expectoration ability, hemodynamic instability, recent esophageal surgery). 3\. Patients with poor short-term prognosis (very high risk of death within seven days or receiving palliative care). 4\. Other organs' failure e.g severe heart, brain, liver, or kidney failure. 5. Tracheostomised patients. 6. Loss of follow up and uncertain 28 day survival.